Parameter passing between two CI applications on the same server

[eluser]WebMada[/eluser]
I continue my thread idea.

I thought to use $_SESSION of PHP because I think that $this->session of PHP cannot be got in other web application, isn't it??
But I think also that $_SESSION cannot be caught in other application?? How do web hosters to avoid that a hosted site steals the session of another site???

My solution is to use database, site 1 stores the information in a specific table and redirects to site 2 which will read it. How do you think about that?